Air bags are inflatable cushion or pillow-like restraint devices positioned in vehicles in front of riders to protect them from pitching forward into solid parts of the vehicle in the event of an accident. They have become well-known safety features in currently available automobiles and the like. Typically, air bag safety systems are incorporated into the steering wheel and dash or instrument panel of a vehicle and are designed to expand automatically and rapidly in the event of sudden deceleration or collision to prevent potentially injurious forward movement of the occupant. Such systems may be operated by release of a stored supply of compressed gas or activation of gas-producing propellant compositions such as azide/oxidizer compositions. The latter involve azide salts or like substances which produce nitrogen or another inert gas when reacted with an oxidizing agent.
To be useful, air bags require a minimum of expansion time, as little as twenty to sixty milliseconds, since they are inflated or expanded slightly before or just after a deceleration or impact. Expansion pressure produced by the inflation of air bags is very high, causing the air pressure in the vehicle passenger compartment to increase very rapidly, possibly causing injury. This problem is particularly severe when multiple air bags, including rear seat bags, are provided. U.S. Pat. No. 3,861,710 (to Okubo) attempts to solve the pressure problem by providing for the incremental or delayed full expansion of an air bag. Somewhat similarly, U.S. Pat. No. 3,862,767 (to Chute), 3,638,964 (also to Chute) and 3,884,497 (to Massengill et al.) are directed to controlling the flow of inflating gas for air bag systems. However, as stated above, and in the Okubo patent, an air bag must inflate within a certain amount of time to be effective. Delaying or lengthening the time required for full inflation to avoid pressure increases may prevent timely or sufficient inflation.
Another problem is that large quantifies of inflating gas may have a harmful, or at least unknown, effect on vehicle occupants. Efforts are made to use inert, nontoxic and noncorrosive gases, but it would be advantageous to reduce the required quantity of inflating gas to a minimal level.
U.S. Pat. No. 5,018,762 (to Suzuki et al.) discloses a fairly representative air-bag device which, in the event of a collision, is inflated by gas flow, but which also obstructs or controls the flow of gas in the air-bag to avoid the flow of gas to the upper portion of the bag. There is no suggestion of how to control or prevent sudden pressure increases in the passenger compartment of the vehicle, or of how to reduce the quantity of inflating gas used.
U.S. Pat. No. 4,536,008 (to Brown, Jr.) discloses an occupant restraining device including an air bag with internal telescoping tubes extending through the air bag and attached to a pelvic and torso engaging means. In operation, a firing assembly detonates a cartridge in a transverse mounting tube. Gases from the cartridge escape into the telescoping tubes, extending the tubes and passing through apertures in the tubes, expanding and inflating the air bag. The air bag may contain one or more flapper valves to enable the intake of air upon the rapid expansion of the bag by the telescoping tubes, to seal the bag upon inflation, and to release pressure from the bag upon depression of the flapper valve by the occupant or rescue personnel. The Brown, Jr. restraint device is mountable only at and deployable from the interior overhead of a vehicle, thereby limiting its application, and does not include an automatic pressure release mechanism.
A problem unaddressed by the Brown, Jr. patent is that the mere presence of an extended length of relatively rigid metal or plastic, i.e., the telescoping tubes, may pose dangers in certain accident situations. The device disclosed in U.S. Pat. No. 3,675,942 (to Huber) avoids this problem by providing an air bag incorporating passageways comprising a space between two skins forming the bag. The passageways are inflated to extend the bag, which has unidirectional valves to permit ambient air to be drawn into the bag as it is extended. There is no disclosure of free-standing inflatable, extending means for extending the bag in a desired shape or direction, nor is there any suggestion of how to release pressure from the passageways or the bag just before or upon impact to provide an enhanced cushioning effect.